Efl_Future actually work with weak reference. So you do not need to
set things to NULL, but you actually need to register the memory location
of the future with efl_future_use.
while in a job we do not have the safety of eo holding us alive and
when we call back the user, he may have deleted the object, releasing
both the object and its private data that we're using.
then keep an extra reference, call the methods and release it.
Efl.Object.event_callback_call no longer calls legacy smart callbacks;
calling only event callbacks registered with the given event description
pointer.
Create the method Efl.Object.event_callback_legacy_call to inherit the old
behavior from Efl.Object.event_callback_call, calling both Efl.Object events
and legacy smart callbacks.
Update all other files accordingly in order to still supply legacy
callbacks while they are necessary.
These interfaces allows generic operations on objects that can store
or provide data, such as a file or a buffer.
With well defined interfaces and events we can create code such as
Efl.Io.Copier, that will link a source with a destination and
progressively copy data as they appear.